Sound control apparatus



March 1,-1932. I Q FARmupl 1,847,935

soUNDcoNTRoL APPARATUS Original Filed April 25, 1921 y) Il Isig* C d s I A n l. 0/ vgNToR I @im BY y ATToRNl-:Y

I tion. A

' Patentea Mat. 1,- 1932'- UNlrEos-TATES YPAT1;1\f1' r OFFICE CLAIR L FAnnAn-D, or ronns'r Hints, NEW YORK, AssIGNon :no LExrorHoNE con.-

' POR-ATION, OFVNEW YORK, N. Y., A CORPORATION OF DELAWARE SOUND CONTROL APPARATUS original ,application flieanpril as, 1921,

` My invention relates to apparatus for the intercontrol or interconversion of electrical energy'and sound for any suitable or desired purposes, asl for example, telephony, phog nography, amplication of sound or of sound- "respresenting electrical energy, or other kin- Y dred or analogous purposes.

The present application isa vdivision of my co-pending application Serial, No. 464,009 l@ filed April 23, 1921.

lln accordance with -my invention ll employ for sound reproductionV or control by sound, in association with a diaphragm or tympanum vrelatively large in diameter as com- 115' pared with'. usual or common telephone or having a direct coaxial connectionwith the diaphragm and which is Vre'ciprocable in the air gap in a path parallel with the polar faces.

Further in accordance With'my invention, the' diaphragm and the electro-magnetic means are vso positioned or disposed relatively to each other'as to form a compact struc- L ture suitable for various purposes, as. for example, portable sound reproducer or tele-I phone transmitter or loud talking receiver.

f lThe invention-is illustrated in the accompanying drawing which is a vertical longitudinal-section, partly in elevation, of soundproducing apparatusembodying my invennferring to the drawing, n f is la diaphragm or tympanum of' suitable material 45 andstructure, such, for example, as disclosed innopkins Patent No. 1,271,5,29Ju1y 2, 1918*., The diaphragm D proper is conical, as indi-.

cated, or 'of other orequivalent formation,

and has i its integral circumferential ringV or y 5 flange a rigidly clamped or held between the Serial No. 464,009. Divided and this application led`0ctober 17, 1925. Serial No. 63,042.

clamping rings b and o secured to each other by any suitable means, as by screws d. The diaphragm D has a portionafwhich forms with the walls of the cone an abrupt bend and thereby constitutes a flexible rif for flexibly connecting the conical portion of the diaphragm to the support. rlhe ring o is provided, if desired, with a pin n which is received in an aperture in the p-ortable or other base member o. Attached to the ring c are the inwardly extending arms e.

lfntegralwith or supported by the arms e is the cup-shaped magnetic field yoke member p disposed well within the concave or hollow side of the diaphragm D. l'llhe yoke member p, and also the arms e when integrall therewith,x may be of cast iron or other suit- 1 able magnetizable material. The central core member g, preferably of Norway.V orlother soft iron, either in solid form or 1n lamlnae vor Wires, is supported at its right endin the back yoke member r forming the closure of the cup member p. V.At-the other end of the cup member p is the circular pole member s,

of cast iron or other suitable magnetizable material extending radially inwardly and approaching the end of the" core g, b-ut spaced therefrom to leave an air 'gap or space within which may vibrate, longitudinally of the axis.

of the conical diaphragm D, a coil or winding M wound circumferentially upon and secured to the cylindrical form or frame t of insulating material having at one end the arms or spider u secured to the pin or rod o, which is secured to the vdiaphragm D at vits center and apex by the clamping nut fw. Disposed within the yoke member 79 andysurroundirrgl the core q' is the magnetizing winding W for producing an intense magnetic field inthe gap betwen the pole members and the core g M. The Winding W is traversed by current in which is disposed'the aforesaid windingv of suitablev magnitude from any suitableI source. The terminals ofthe Winding W are connected to the binding posts a1, and the' terminals of the coil M are connected by liexible conductors y, y, lextending through a'bore in the core gtothe binding posts a, a, which,- and th'ebinding posts ai, m, are carried upon the block a1, of insulating material, secured `to the member 1'.

When the winding W is traversed by current so producing an intense magnetic field for the coil M, and when the coil M is traversed by fluctuating or varying electric current, thecoil M will be with correspondingly variable degree attracted and moved axially of the conical diaphragm D and transmit thereto corresponding vibrations, which vibrations are substantially distortionless as regards their representation of the wave form of the electric current through the coil M,

and such vibrations of the diaphragm D are without substantialdistortion converted into v sound Waves in the surrounding air, which sound waves represent without substantial distortion the variations in the current traversing the coil M. In this aspect the structure described is a telephone receiver VJfor producing amplified sound waves which ma readily be heard at substantial distances fyrom the dia hragm D.

l Clbnversely, .with the windingW energized, upon production of speech or sound waves in the vicinity of the diaphragm D it will vibrate in substantially distortionless accord with those 'sound waves and -transmit the vibrations to the coil M, whose corresponding movements inthe intense ma netic fieldv will cause generation inthe coil of electric currents whose wave forms are in substantially distortionless accord with the utteredspeech or sound waves. In this aspect the apparatus is a telephone transmitter and has decided advantages over the ordinary carbon or other microphone used in telephony in that the wave form of the sound-representing current corresponds substantially exactly with the uttered speech or sound waves.

For purposes both of reception and ltransmission it is desirable that the total mass or inertia. of the Acoil M, support u and pin 'v shall b e as small as possible in order that the diaphragm D shall be loaded or damped as little as possible, and thereby avoid modication or disturbance of its own characteristics.

It is further advantageously characteristic ofthe N"structure above described that the forces exerted by the coil M upon the diaphragm D, or vice versa, are, as to their direction, co-axial with the cone D, and originate close thereto and are not transmitted through long or massive intervening mem'- bers.

It will be understood that the structure described may be utilized for other or various purposes, as for example, for converting into sound audible throughout aroom radio tele'- graphic or telephonie signals, as when connecting the coil M in place of or in association with" the telephone receiver commonly employed in radio receiving apparatus.

In general, when there is to be control or conversion into sound by or' from electric energy, or vice versa, and which I term intercontrol or intcrconversion,itis desired, that the mass or inertia f the movable structure of the electrical apparatus and its mechanical connection to the diaphragm D shall'be as small as possible vconsistent with desired magnitude of the vibratory forces involved.

A loudspeaker constructed as herein disclosed, that is, one having a direct-acting diaphragmcomprising a substantially rigid central portionconnected to a support by a flexible rim and actuated by an armature coaxially connected with the rigid portion of the diaphragm and moving in a path lpar-v allel'with the polar faces has the following important advantages; the total elastic restoring force, localized in the diaphragm and its flexible rim, may be kept down to that small and predetermined value that will cause quencies. The armature by reason of its lreedom from elastic restoring force of its own adds nothing tothe elastic restoring force o the diaphragm and does not upset ,or disturb the advantageous characteristics oi the diaphragm. f

Radio broadcasting andreceiving appaf ratus, including amplifiers, has been developed to the point where it is possible to obtain amplified currents, representing the original sounds, practically free from distortion. The elements of the above described combination coact to produce a distortionless apparatus capable of receiving these undistorted currents and reproducing them in a distortionless manner.

I claim:

1. The combination with a conical tympanum of a coil substantially coaxial therewith and disposed within the sameon the concave side thereof, a field magnet for said coil disposed on the concave side of said tympanum within the same, and an axial connection between said coiland the apex of said tympanum. 2. The combination with a conical tympanum, of a support to which the periphery of said tympanum is secured, afield magnet support extending from said support toward the axis of said tympanum on the concave side thereof, a ield magnet carried by said last named support, a coil coaxial with said tympanum disposedin the field of said magnet,

and a connection from said coil to the apex 12 CLAIR L. FARRAND. 

